X-rays showed foreign bodies in his stomach and intestines and he was rushed into emergency surgery, where our vets removed two tennis balls.

Just a couple of weeks later, three-year-old bull mastiff Ryder came to us because he had been feeling off his game for a while.

Double fault for poorly Ryder

When he was sick, bringing up not one, but two tennis balls, owner Gillian Murison thought he would be back to his usual self.

However, when it was clear that Ryder was still not well, she brought him to the Blue Cross hospital in Victoria. X-rays revealed that there was yet another tennis ball in Ryder’s stomach, which vets operated to remove.

Gillian said: “When they found the third ball, I almost cried with relief – I was so worried about him.

“I never give Ryder tennis balls to play with, so I can’t understand how this happened – he must have found them in the park. I’m so happy that he is feeling well again.”

Tennis balls can be dangerous for large dogs

Blue Cross vet Nigel Smith says: “It is unusual for us to remove quite so many tennis balls in such a short space of time, but sadly it’s not an uncommon problem.

“We would advise owners of large dogs not to give them tennis balls to play with. Because of their size, it’s really easy for them to swallow the balls when they are thrown, or they could even get stuck in their throats.”

Blue Cross recommends playing with bigger dogs using safe toys such as a Kong rubber toy on a rope or a football.

Last year Blue Cross performed more than 10,500 operations on sick and injured pets and carried out more than 65,000 consultations, funded entirely by donations.